On Thu, Oct 24, 2024 at 08:26:11PM +0530, Hardik Gohil wrote:
From: Mark Brown broonie@kernel.org
[ Upstream commit 6098475d4cb48d821bdf453c61118c56e26294f0 ]
Currently we have a global spi_add_lock which we take when adding new devices so that we can check that we're not trying to reuse a chip select that's already controlled. This means that if the SPI device is itself a SPI controller and triggers the instantiation of further SPI devices we trigger a deadlock as we try to register and instantiate those devices while in the process of doing so for the parent controller and hence already holding the global spi_add_lock. Since we only care about concurrency within a single SPI bus move the lock to be per controller, avoiding the deadlock.
This can be easily triggered in the case of spi-mux.
Reported-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Hardik Gohil hgohil@mvista.com
This fix was not backported to v5.4 and 5.10
Along with this fix please also apply this fix on top of this
spi: fix use-after-free of the add_lock mutex commit 6c53b45c71b4920b5e62f0ea8079a1da382b9434 upstream.
Commit 6098475d4cb4 ("spi: Fix deadlock when adding SPI controllers on SPI buses") introduced a per-controller mutex. But mutex_unlock() of said lock is called after the controller is already freed:
Now both queued up, thanks.
greg k-h